Strange

If they are in free fall, then they are not accelerating. And you are no longer talking about the twins paradox. What is the point of leaping around from one random scenario to another?

What does that mean? Does someone accelerating away look the same as you accelerating away from them? Yes. But so what.

I just came across this term. A style of trolling that may be familiar: https://en.wikipedia.org/wiki/Sea_lioning http://wondermark.com/1k62/

Ipsos have carried out a survey of what people perceive about the world, versus how it is. In general, particularly when it comes to crime and terrorism, people think things are much worse than they are. The ideas about alcohol consumption by country are quite amusing: stereotypical and generally wrong (you will probably be surprised by the country with the highest alcohol consumption). https://perils.ipsos.com/slides/ And, perhaps not surprisingly, the countries where people are most confident about their answers are also the countries where they are most wrong.

Stern-Gerlach? But there isn't really any "classical" evidence, because it is a quantum effect, so I'm not sure what you are looking for.

I'm guessing that, behind the scenes, the NRA is pushing to have new laws passed making it illegal for shops and individuals to apply their own (more restrictive) rules when selling guns. And maybe make it illegal for investment companies like Black Rock to offer investments that "discriminate" against gun manufacturers. And making criticism of the NRA equivalent to blasphemy or treason.

Before someone comes back and claims this shows how inaccurate climate models are, it is probably worth highlighting that: 1. It is just one model. No one plans (or achieves scientific consensus) based on a single model or one experiment. 2. It is more than 35 years old. A lot has been learned since then and newer models take many more factors into account. 3. The relative difference in temperatures is correct.

No If you are sitting in your car with the engine off and watch someone accelerate away, are you pressed back in your seat? (No) if you start your engine and accelerate sea, are you pressed back in your seat? (Yes) So, no it is not relative/reciprocal.

It assumes that one undergoes acceleration while the other doesn’t. Still don’t see how this relates to your question about energy (although I assume the less aged twin will have used energy to accelerate)

It is also a matter of how accurate you need to be.For example, satellite TV receivers don't care about relativistic effects, but GPS receivers have to.

I found out the other day that the NRA has passed legislation (*) that means government funding cannot be used to research many topics related to gun deaths (like, is mental health a risk factor). And that it is not possible to have a searchable database of gun owners. People have to search the paper records - they can be scanned but if that is done, they can't be OCR'd because that would make them searchable. (*) A slight exaggeration. They obviously didn't pass the legislation. They paid others to do it for them.

We can't see any photons from that time. They were all thermalised over the the following 380,000 years.

Expansion (not inflation) has stretched the photons that were around at the era of recombination and they form the cosmic microwave background. (There is no mechanism that I know of for some photons to be unaffected by this.)

That shouldn’t be a surprise to anyone but seeing him follow through on it might have an effect.

Well spotted. (I assumed he was talking about the Planck relationship and didn’t notice he said “Heisenberg” and got the equation wrong!)

I guess you mean the observer effect: https://en.m.wikipedia.org/wiki/Observer_effect_(physics)

I can’t see any connection with the twin paradox, which says nothing about energy.

Note that this refers to wavelength, not length in general. But your question still applies. You are right that the energy of a system will depend your speed relative to it. This applies whether you consider the kinetic energy of a massive body or the wavelength of light from a source. Both of these are observer dependent: different people will see different kinetic energy or different wavelength depending on their relative speed. However, energy is still conserved because it takes energy to change your speed. (Note that this gets more complicated once you start considering things like gravitational or cosmological red-shift because the definition of energy, and whether it is conserved, is not simple in GR)

What?

But if Doppler shift weren’t explained by relative motion (which is kind of inherent in the nature of waves) then you would need to explain why not. And does the same apply to sound? (I have seen some odd ideas in my time, but denying Doppler shift is a new one.) Are we still talking about Doppler? How is that relevant to, say, terrestrial radar system? The Doppler effect is based on all those. There is just logic. This is like asking “who’s arithmetic” Are you under the misapprehension that logic is a subjective thing? Are you confusing it with common sense.

And writing. One of the three(?) places where writing was invented. (Maybe not the earliest, but it was done independently of the others.)

Well, I'm not going to get into a discussion about whether quantum theory is correct or not. As far as I know, there is no limit on the distance over which entanglement can exist; even beyond the observable universe. But I haven't ever seen anything about that. Exactly. But trying to visualise how that woks in 3D is a bit tricky.

I guess he is just angry and decided to blame the Chinese. Or something.

I assume the whole thing is made from magnetite (the Chinese are very good at working difficult stones; look at some of their jade work - a material that cannot be carved). And if it is heavier, there is more magnetite and so a stronger magnet. But there is probably some ideal balance between size and functionality. The other good thing about the spoon shape as a balance is that it doesn't depend on the base being perfectly level. Reported?

Which is why his question makes no sense.